This invention relates to disease resistance in plants.
Grapevine fanleaf virus (GFLV) is a grape nepovirus, which is transmitted from plant to plant by the dagger nematode, Xiphinema index. GFLV is the agent responsible for grapevine fanleaf disease, which occurs worldwide. The disease is named for the fan-leaf shaped appearance of GFLV-infected leaves. It is one of the most damaging and widespread diseases of grapevine. Symptoms of GFLV infection include abnormal shoot morphology and discolorations of the leaves, yielding a fan-like appearance (Agrios, Plant Pathology, 3rd Edition, Academic Press, 1988, pp. 687–688). In addition, fruit production of infected vines is low, with grapevines producing small bunches having abnormal fruit set and ripening. Ultimately, infected grapevines degenerate and die.
Long range spread of GFLV is believed to be by use of infected planting material. While the natural host range is thought to be restricted to grape, GFLV is also transmissible to a wide range of herbaceous species by sap-rubbing inoculation. Chenopodium quinoa is a useful diagnostic species for the virus. In general, GFLV isolates are antigenically uniform and diagnosis by ELISA is a standard procedure.
Current strategies for controlling grapevine fanleaf disease and other nepovirus-induced diseases in vineyards include nematode control (for example, soil fumigation and use of other pesticides), breeding rootstocks for resistance to nematode feeding, breeding grapevines for resistance to GFLV, and planting certified disease-free grapevines.